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(No Model.) a 2 sheet -sheet 1. 1VI. G. KELLOGG. MULTIPLE SWITCH BOARDFOR TELEPHONE EXCHANGES.

No. 427,087. Patented May 6, 1890.

(No Model.) I 2 Sheets-Shed 2. M. G. KELLOGG.

MULTIPLE SWITCH BOARD FOR TELEPHONE EXCHANGES. I No. 427,087. PatentedMay 6, 1 890.

UNITED STATES PATENT FFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS.

SPECIFIQATION forming part of Letters Patent No. 427,087, dated May 6,1890.

Application filed June 28,1888- Serial No. 278,423. (No model.)

To all whom it may concern:

Be it known that I, MILO G. KELLOGG, of Chicago, Illinois, have inventedcertain new and useful Improvements in Multiple Switch- Boards forTelephOneEXchanges, of which the following is a full, clear, concise,and exact description, reference being had to the accompanyingdrawings,forming a part of this specification.

My invention is an improvement in the 1nultiple-switch-board systemdescribed in my application for patent filed December 8, 1887, No.257,317, now patented, No. 424,310, dated March 25, 1890.

The-principal advantages obtained in the system which I shall nowdescribe as com-' pared with the system described in said applicationare a reduction in the number of switch-plugs and cords required at thecentral office and in the number of calling-keys or amount of signalapparatus required at the subscribers stations.

In carrying out my invention I divide the subscribers lines which centerat an exchange-office into two divisions or classes. I also divide theswitch-boards required for the operation of the exchange into twosections. On each board of one section Iplace a springjack or similarswitch for each line of one class, and for each of said lines I alsoplace on a switch-board of the other section a spring-jack switch. Oneach board of the other section I also place a spring-jack or similarswitch for each line of the other class, and for each of said lines Iplace on a switchboard of the first-mentioned section a springjackswitch. The said spring-jack switches of the lines, of which there isonly one in each section for the line, are distributed in approximatelyequal numbers among the switch-boardsof their section. These switches,as will hereinafter appear, are to be used in answering theirsubscribers calls and in con-' necting their subscribers lines, inanswer to their calls, to other subscribers lines. They may therefore bedesignated as answering spring-jack switches. The other switchesof theexchange (those of which there are one for each line on each board ofits section)are used in making calls to and connections with their lineswhen the lines are wanted. They may therefore be designated as callingspring-jack switches. Part of the lastdescribed switchesto wit, one foreach linemay also be used in answering their subscribers calls and inconnecting their subscribers lines, in answer to their calls, to othersubscribers lines. Such switches may also be designated as answeringspring-jack switches, and such switches of a section should bedistributed in approximately equal numbers among the boards of asection. From the above it will appear that each line of an exchange hasacalling-switch on each board of a section and an answering-switch onone board of both sections, and that one of the calling-switches of aline is also an answering-switch of the line. The number of switchesused for a line is therefore one more than the number of switch-boardsof the section on which are its calling-switches. In some arrangementsit might be found convenient to use a special answering-switch for aline in the section in which its callingswitches are located. Shouldthis be the case, they can readily be provided.

For each line I provide two signal-receiving instruments or annunciatorsat the central office, whereby the subscriber may signal to the centraloffice. These annunciators of a line are located where theansweringswitches of the line are located, and consequently at twoboards of the exchange, one

board in each section. The operator at each of these boards maytherefore know when the subscriber has signaled her.

On each board I also provide test circuits and apparatus, whereby theoperator may test any line which is connected to all the switchboards ofthe section to which her board belongs, and determine whether or not theline is switched for conversation at any other board of the exchange.

On each board I also provide operators systems of pairs of cords withplugs, including operators telephone, calling-generator, switches, andcircuits for same, one system for each operator, of any usual form andconstruction, whereby the operator may conveniently connect hertelephone into circuit with any line which has its answering-switch andsignal-receiving apparatus at her board, and

may connect said line for conversation with any line which has itscalling-switch at her board.

At each subscribers station I provide signaling apparatus, whereby thesubscriber may signal to the operators at the two boards where thesignal-receiving apparatuses of his line are located. I prefer to havethe subscribers signaling apparatus and the signalreceiving apparatus ofhis line at the two boards so constructed and placed with reference toeach other that the subscriber may signal to either of the boards atwill without his attracting the attention of the operator at the otherboard.

At each subscribers station is also the usual telephone apparatus andcircuits adapted to the particular exchange system employed. The linesmay be divided into approximately equal classes and the boards intoapproximately equal sections.

It will be seen from the above general description of the system thatasubscriber may signal to one section of the exchange and may obtainconnection with any line of the exchange which has its calling-switchesin that section, and by signaling to the other section may obtainconnection with any of the other lines of the exchange.

In the usual form of multiple switch boards one spring-jack switch isrequired for each line on each board of the exchange. It is apparentthat with the organization described above only about one-half thatnumber of switches would be required.

My invention as a Whole is applicable to all the various systems oflines and of testing which may be employed in multiple-switchboardsystems.

The systems of apparatus and of testing which I have shown in thedrawings, and which I will now describe in detail, are adapted to asystem of single-circuit lines where the lines are normally grounded atthe central office and at the subscribers stations.

In the drawings, Figures 1, 1, 1 and 1 represent front views of sectionsof four switch-boards of a multiple exchange system embodying myinvention, the two former belonging to one section of the boards and thetwo latter to the other section of the boards. In Fig. 2, A, A 13, and Brepresent sectional views of said boards, respectively, each asindicated by the line d c, with all the 1nain-lin-e apparatus andcircuits necessary to illustrate my invention. Fig. 3 shows a diagram ofan operators cord system which may be used in connection with eitherboard. Fig. 4 shows a diagram of an operators test apparatus which maybe used in connection with either board. Fig. 5 shows in diagram thesubscribers-station apparatus. Fig. 6 is an end View of thegenerator-shaft at the subscribers station, with two contact-springsbearing one on each side of the shaft, and of the insulatedcontact-piece of the shaft. Fig. '7 shows in detail thecalling-annunciators used at the central office.

I In the drawings like parts and apparatus in the different figures areindicated by the same letters of reference. G in each case representsthe ground-connection.

In the drawings, 0 c, &c., represent rubber strips, on which the metalparts of the springjack switches are mounted. These strips may be longenough to receive any convenient number of spring-jack parts.

Z Z are rectilinear holes through the fronts of and at the edges of thestrips adapted to receive the switch-plugs. The contact-sprin gs g g aremounted to the rear of and are parallel to the holes H, to. which theybelong, as shown. The contact-points 7L 72., on which thecontact-springs or spring-levers g'g normally bear, pass through therubber strips, as shown. These contact-points piece 7L, and also acontact piece or extension 7L, as shown, along to the front of the pointand along the lower face of the hole. Toward the front of theswitch-holes and along their lower faces I place the contact-pieces 'L'2', as shown. These pieces come in proximity with but do not touch thecontact-pieces h" of their switches, and extend far enough to the frontof their respective holes, so that test-plugs may be applied to them.The switch-plugs are substantially as shown and as will hereinafter bedescribed.

The several parts mentioned above are so made, shaped, arranged, andadjusted that when a switch-plug is inserted'into a switchhole it raisesthe spring-lever in the .rear of the hole from the contact-point onwhich it normally bears, and the flexible cord of the plug is connectedwith the spring-lever, while the contact-point and the contact-piece 'L'of the switch are electrically connected through the medium of the piecemof the switchplug, which then touches both i and h of the switch.

Each section of the rubber strip, with its spring-lever, contact-point,contact-pieces, and the hole, all arranged and operating as above, andas shown, maybe called a springjack switch. The rubber strips are placedone above the other, as shown. The lower edge of one strip thereforeprovides the upper edges of the holes in the strip which is below it.The holes may be of any convenient shape adapted to the shape andarrangement of the parts used.

The calling-annunciators or signal-receiving instrumentsone for eachline in each of the two sections of the exchangeare marked to in thedrawings, and those which are shown are located at the boards where thecalls of their lines are to be answered. These annunciators arepolarized annunciators, and their construction is shown in greaterdetail in Fig. '7. Each of these annunciators responds or indicates whenone polarity of current passes over its line and does not respond whenthe have each a connecting- ITO the piece 0, and thereby form connectionbetween the cords and the ground. The parts of an operators cord systemshould be conveniently mounted at the board where it is to be used, soas to allow the required operations of the system. The connections ofthe system are substantially as shown. The operatidns of the system inanswering calls, making connections, and attending to the other exchangeoperations will be apparent to those skilled in the art.

The operators test system shown in Fig. 4 consists, essentially, of atest wire or circuit in which is a test-receiving instrument (which maybe a magneto-telephone) and a suitable test-battery, said test wire orcircuit being grounded at one end and terminating at its other end in atest-plug with a flexible conducting-cord adapted to be brought intoconnection with any contact-piece t' of the board where the test systemis located. In the figure, T is the test-plug, I is the test-receivinginstrument, and B is the test-battery. The operator at each board shouldbe provided with one cord system and one test system. scription of theapparatus and circuits which has been given that when any line of theexchange is switched for conversation at any board where it has a switchall the contact pieces it of all the switches of the line are crossed orconnected with the ground, such connection being due to the crossing ofthe piecei with the piece h of the switch when the connection is madeand the fact that all the pieces it of the switches of a line areconnected together. lVhen the line is not switched at any board, all thepieces 2' 2' of its switches are open to the ground. \Vhen an operator,therefore, brings her test-plug T in contact with piece 'i at her board,and the line to which it belongs is switched at another board, therewill be a complete circuit established in which is her test-receivinginstrument and test-battery, and her instrument will sound. If the lineis not switched at any board, there will be no such complete circuit andthe instrument will not sound. The operator can thereby determinewhether or not the line is in use at another board.

The apparatus shown and described will enable an operator to test onlysuch lines as have their switches on her board, and these areapproximately about one-half the lines of the exchange. It is evidentthat facilities for testing such lines are sufficient, as it is onlywith them that she is required to switch to when they are called.

To carry out the organization it is necessary that each subscribershould be able to determine whether or not he is to press hiscalling-key when he calls for connection with any other subscriber. Toaccomplish this the subscribers whose lines belong to one class may beindicated by some designation in the exchange list-as, for instance,their numbers may all be prefixed by the letter A. The

It will be seen from the desubscribers which belong to the other classmay also be designated in some manner-as, for instance, by the absenceof any prefix or special mark. All the calling-keys might be marked withthe letter A. The apparatus and lines could be so connected that when asubscriber desires connection with any line designated by the letter Ahe is to operate his generator while pressingon his calling-key markedA. WVhen he desires connection with any line of the other class, he isto operate his generator Without pressing on the calling-key. Thissystem of calling either board at will to which the subscriber may beconnected therefore requires but one calling-key, and it requires thesubscriber to press on the key only when he is calling one board.

It will be seen from the description of the main-line circuits andapparatus and of the operators cord system as given that whentwosubscribers lines are switched together at any board of the exchangeby the insertion of the two plugs of any pair of cords into the switchesof the line at that board the two calling-annunciators of each line arecut off or disconnected from the circuits of the line, and the operatormay, by the use of the switch Y, loop the clearing-out annunciator 1)into the combined circuit of the lines. The number of pairs of cordsneeded for the system will depend on the number of connections which areliable to be required at one time in the exchange. As a general thingonly about one pair of cords to every eight or ten subscribers lineswill answer.

I claim as my invention and desire to secure by Letters Patent- 1. In atelephone-exchange system, the combination of telephone-lines dividedinto two classes, multiple switch-boards for said lines divided into twosect-ions, switches for said lines, a switch for each line of one classon each board of one section and on a board of the other section, and aswitch for each line of the other class on each board of said othersection and on a board of the first-mentioned section, and pairs ofswitch-plugs with cords, whereby an operator at anyboard may byinserting the two plugs of a pair into the two switches of,thelines'eonnect together any two lines which have their switches at herboard, substantially as set forth.

2. I11 a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, switches for said lines, aswitch for each line of oneclass on each board of one section and on a board of the other section,and a switch for each line of the other class on each board of saidother section and on a board of the first-mentioned section,annunciators for said lines, tWo annunciators for each line, one locatedat a board in the section in which its line has a switch 011 each boardand the other located at the board in the other section where the switchof the line is located, and pairs of TOC other polarity of currentpasses over the line. The two annunciators of any given lineone in eachsection of the exchange-are so constructed and so connected into thecircuit of their line that one of them will respond to one polarity ofcurrent and the other will respond to the other polarity of current.

I have represented two lines as connected to the boards of the exchange,one line of each class. One line is marked line A and the other ismarked line 13'. Line A after entering the office, passes successivelythrough its switches on boards A and A thence through itsanswering-switch, (marked ct on board B',) in each case going to thespring-lever first, thence through its annunciators w w on boards A andB, and thence to the ground, all as shown. Line B, after entering theoffice, passes successively through its switches on boards B and Bthence through its answering-switch, (marked Z) on board A in each casegoing to the spring lever first, thence through its annunciators w w onboards A and B and thence to the ground, all as shown. All thecontact-piecesi dot the switches of a line are connected together, as isshown. The lines are also grounded after passing through theirsubscribers station apparatus.

In the diagram of the subscribers station apparatus shown in Fig. 5, 1is the telephoneswitch, 2 is the signal-receiving bell, 3 is thecalling-generator, i is the operators telephone, and 7c is acalling-key. The generator is constructed with the usual automaticdevice, whereby it is shunted or switched from the line-circuit whilenot operated. The insulated contact-piece on the shaft of the armature,to which is connected one end of the armature-wire, and which conductsthe generated current to the line through the stationary spring-contact(or contacts) provided for it, is a half-circle, the remaining part ofthe circle being an insulation, as shown. I provide two stationaryspring contact-pieces, as shown, each bearing on thediametrically-opposite part of the circle of the shaft of which said.insulated contactpiece is a part. The key is provided with two pairs ofcontact-points, as shown, one pair being normally closed and the otherpair normally open, and when the keyis depressed the normally-open pairof contacts is closed and the normally-closed pair is opened. Theconnection of the key to the contact-sprin gs of the generator and tothe line-circuit is as follows and as shown: The spring-lever, whichformsone of the contacts of each pair of contact-points, is connectedwith one side of the main-line circuit. The two other contact-pieces ofthe pairs of contact-points are connected to the two contact-springs,respectively. As stated above, one end of the armature-wire is connectedwith half-circle contact-piece 011 the generator-shat t, 011 which thesprings alternately bear when the generator is being turned. The otherend of the armature-Wire is connected with the other side of themain-line circuit. The automatic shunt device mentioned before may shuntthat part of the circuit containing the armature-wire and the key whenthe generator is not being turned.

It is well known that when magneto-generators are turned and operated acurrent'of one polarity is generated during one half of the revolutionof the armature and a current of the other polarity is generated duringthe other half of the revolution of the armature. It will be apparentfrom the description of the subscribefis-station apparatus which hasbeen given, and from the circuits, that when. the generator is beingoperated and the key remains in its normal position the armaturewire isin circuit through one of the contactsprings, and that only, and acurrent of one polarity will be sent to the line, and that when thegenerator is being operated and the key is depressed the armature-wireis in circuit through the other contact-spring, and that only, and acurrent of the other polarity will be sent to the line. The subscribercan therefore at will send currents of either polarity to line, as hedoes not or does press on the calling-key. \Vhen his line is providedwith two calling-annunciators which respond to currents of oppositepolarity, as indicated, one annunciator being located ata board in onesection of the exchange and the other annunciator being located at aboard in the other section of the exchange, he can at will call theoperator at either board and not disturb the other operator.

The operators cord system shown in Fig. 3 has a pair of cords withswitch-plugs, acalling-key, a looping-in switch, and a clearingoutannunciator for the same and the usual telephone and calling-generator.Only one pair of cordsand plugs with its special apparatus is shown.Others could be added in a manner which will be apparent to thoseskilled in the art. I) D are the switch-plugs connected to the cords andadapted to beinserted into the line-switches. m m are the metal piecesof the plugs, adapted to come in contact with the spring-levers g g ofthe switches and connect the levers with the cords of the plugs. m m aremetal pieces of the plugs, adapted to come in contact with the pieces h"and 1'. of the switches when the plugs are inserted into them andconnect said pieces together. Y is the looping-in switch for the pair ofcords, and v is the clearing-out annuncia'tor. B is thecalling-generator, and 25 is the operators telephone. \Vhen the plugsare used, they should be inserted in such a position as to make theconnections as above described. a 'n are the rubber insulations of theplugs. The pieces m m extend to the bottom of the plugs, as shown, andare adapted to rest on the metal strip 0, as shown, and normally connectthem with the ground. WVeights in the usual manner or similar devicesmay be used to bring the bottoms of the plugs onto switch-plugs withcords at each board, whereby an operator at the board may by insertingthe two plugs of a pair into the two switches of the lines connecttogether any two lines which have their switches at her board,substantially as set ,forth.

3. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, switches for said lines, a switch for each line ofone class on each board of one section and on a board of the othersection, and a switch for each line of the other class on each board ofsaid other section and on aboard of the first-mentioned section,signaling apparatus whereby any subscriber may at will signal to theoperators at two boards of the exchange, one boardin each section, andone of said boards-that one on which is the switch of the subscriberslinein the section where there is but one switch for the line, and pairsof switch-plugs with cords at the boards, whereby the operator at anyboard may by inserting the two plugs of a pair into the two switches ofthe lines connect together any two lines which have their switches ather boards, substantially as set forth.

4. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for saidlines dividedinto two sections, switches for said lines, a switch for each line ofone class on each board of one section and on a board of the othersection, and a switch for each line of the other class on each board ofsaid other section and on a board of the first-mentioned section,polarized annunciators for said lines, two for each line and in thecircuit of their line, one of the annunciators of a line indicatingwhena current of one polarity passes through it and the other indicatingwhen a current of the other polarity passes, the two annunciators beinglocated at two boards of the exchange, one board in each section, andone of said boards-that one on which is the switch of the linein thesection where there is but one switch for the line, asignaling-generator at each subscribers stat-ion, switching apparatuswhereby any subscriber may at will send a current of either polarityover his line, and pairs of switch-plugs with cords at eachboard,whereby the operator at any board may by inserting the two plugsof apair into the two switches of the lines connect together any twolines which have their switches at her board, substantially as setforth.

5. In atelephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switclrboards for said lines dividedinto two sections, switches for said lines, one switch for each line ofone class on each board of one section and one switch for each line ofthe other class on. each board of the other section, said switches beingfor making connections with their-lines when they are called for, andwhich may therefore be designated as calling-switches? also two switchesfor each line, one switch on a board of each section to make connectionwith its line when its subscriber calls, and which may therefore bedesignated as an answeringswitch, and pairs of switch-plugs with cordsat each board, whereby the operator may by inserting the two plugs of apair into the two switches of the lines connect any line which has itsanswering-switch at her board with any line which has a calling-switchat her board, substantially as set forth.

(3. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, switches for said lines, one switch for each line ofone class on each board of one section and one switch for each line ofthe other class on each board of the other section, said switches'bemgfor making connections with their lines when they are called for, andwhich therefore may be designated as calling-switches, also two switchesfor each line, one switch on a boardof each section to make connectionwith its line when its subscriber calls, and which may therefore bedesignated as an answeringswitch) two annunciators for each line, oneannunciator located at a board in each section and at the board of thesection where the answering-switch of the line is located, and pairs ofswitch-plugs with cords at each board, whereby the operator may byinserting the two plugs of a pair into the two switches of the linesconnect any line which has an answering-switch and an annunciator at herboard with any line which has a calling-switch at her board,substantially as set forth.

7. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, switches for said lines, one switch for each line ofone class on each board of one section and one switch for each line ofthe other class on each board of the other section said switches beingfor making connections with their lines when called for, and which maytherefore be designated as calling-switches; also two switches for eachline, one switch on a board of each section to make connection with itsline when its subscriber calls, and which may therefore be designated asan answering-switch, signaling apparatus whereby a subscriber may atwill signal to either board where one of its answering-switches islocated, and pairs of switch-plugs with cords at each board,whereby theoperator may by inserting the two plugs of a pair into the two switchesof the lines connect any line which has an answering-switch at her boardwith any line which has a calling-switch at her board, substantially asset forth.

8. In a telephone exchange system, two switch boards, a telephone lineconnected with said boards, and two annunciators in the circuit of saidline, one at each board, said annunciators being adapted to respond tocurrents of different character, in combination with a source ofelectric energy, and a calling-key at the subscribers station withcontacts to send a proper current to line to operate one of saidannunciators when said key is in the normal position, and contacts tosend a current to line to operate the other annunciator when the key ismoved or depressed.

9. I11 a telephone exchange system, two switch boards, a telephone lineconnected with said boards, and two polarized annunciators in thecircuit of said line, one annunciator located at each board, oneannunciator indicating when a current of one polarity passes through itand the other annunciator indicating when a current of the otherpolarity passes, in combination with a signalin g-generator at thesubscriberss station, an d a calling-key with contact-points to send acurrent of one polarity to the line when the generator is operated andthe key is depressed, and to send a current of the other polarity toline when the generator is operated and the key is not depressed,substantially as set forth.

10. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, a switch for each line of one class on each board ofone section and on a board of the other section, and a switch for eachline of the other class on each board of said other section and on aboard of the first-mentioned section, each line passing successivelythrough its switches on the different boards and thence to ground, andpairs of switch-plugs distributed among the boards, said plugs of a pairbeing connected by flexible conducting cords and adapted to be insertedinto the switches at their board, and when a plug is inserted todisconnect the line to which the switch belongs and connect it with theconducting-cord of the plug, substantially as and for the purpose setforth.

11. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, a switch for each line of one class on each board ofone section and 011 a board of the other section, and a switch for eachline of the other class on each board of said other section and on aboard of the first-mentioned section, two annunciators for each line,said annunciators of a line being at two boards of different sectionsand where the line has switches, each line passing successively throughits switches on the different boards, thence through its twoline-annunciators and thence to ground, and pairs of switch-plugsdistributed among the boards, said plugs of a pair being connected byflexible conducting-cords and adapted to be inserted into the switchesat their board, and when a plug is inserted to disconnect the line towhich the switch belongs from its annunciators and the ground andconnect it with the conducting-cord of the plug, substantially as setforth.

12. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, a switch for each line of one class on each board ofone section and on a board of the other section, and a switch for eachline of the other class on each board of said other section and-on aboard of the first-mentioned section, two annu nciators for each line,said annunciators ot' a line being at two boards of different sectionsand where the line has switches, each line passing successively th roughits switches on the different boards, thence through its twoline-annunciators and thence to ground, and pairs of switclrplugsdistributed among the boards, said plugs of a pair being connected byflexible conducting-cords and having a clearing-out annunciator in thecircuit between them, said plugs being adapted to be inserted into theline-switches at their board, and when inserted into two switches todisconnect the lines from their annunciators and the ground and connectthem with the conducting-cords of the two plugs, respectively,substantially as set forth.

13. In a telephone-exchange system, the combination of telephone-linesdivided into two classes, multiple switch-boards for said lines dividedinto two sections, a switch for each line of one class on each board ofone section and on a board of the other section, and a switch for eachline of the other class on each board of said other section and on aboard of the first-mentioned section, switchconnecting apparatus wherebyan operator at any board may connect together any two lines which havetheir switches at her board, and switch-testing apparatus whereby shemay test any line which is connected to all the boards of her sectionand determine whether it is switched for use, substantially set forth.

MILO G. KELLOGG.

Witnesses:

\VALLAOE L. DEwoLF, MILTON HEAD.

